High-g centrifuge



March 29, 1949- G. B. ENGELHARDT 7 HIGH-G CENTRIFUGE Filed Nov. 30, 19452 Sheets-Sheet 1 I Q Ill,

25 zaawzwww 23 George E-En5e]harcfi. 1

Patented Mar. 29, 1949 ill'l' ribs HIGH-G CENTRIFUGE ApplicationNovember 30, 1945, Serial No. 532,067

(Cl. 73l67 Claims.

The invention relates to improvements in centrifuges, particularly toultra high g centrifuges and a, method of simulating acceleration forcessuch as involved in ordnance projectiles when fired.

It is also an object to improve the construction and functions of highspeed centrifuges in novel ways contributing to an important extent tofacilitating the use of such devices for conventional purposes as wellas for special purposes, and enabling higher accelerations thanheretofore practicable.

It is an important object to enable the counterbalancing of test obiectsor specimens with nicety so as to eliminate vibration which might resultfrom differences in weight of specimen and counterweight, or differencesin radius of test specimens and counter weight. A most impellingattainment in View leading to the invention in one aspect, is to enablesuch accurate counterbalancing to be effected and adjusted at willduring the operation of the centrifuge.

It is also a desideratum to enable-constant optical observation of anobject or specimen throughout the test thereof in the device embodyingthe apparatus of the invention. instead of requiring stoppage foradiustment. This is highly valuable in observation of deformations ofresilient specimens or initiation of functions of mechanical devicesunder acceleration, as well as'in observations of separations of fluids,fluids and solids, or occlusions, etc. It is a specific purpose topresent a novel means for enabling such observations, and particularly anovel stroboscopic system.

A further impelling motive for the invention is to enable the making ofcertain and varicusmeasurements while the specimen is under test in anovel way.

Another novel attainment of the invention resides in the manner ofenabling direct readings at every moment, of acceleration to which anarticle is being subjected, in terms which may be transferred toequations, or which are those customarily used in specifications ofrequirements, or tolerances for various manifestations in specimens,samples, etc. It is a related aim to enable the verification of theaccuracy of readings relating to speed and acceleration at any instantin the operation of the apparatus by simple optical observation.

A highly important of the invention is to present a method wherebydevices required to function in a projectile at a given acceleration maybe tested and demonstrated by similar force,

While being constantly observed and their responses made clearlyapparent to the observer.

It is an animating motive to provide a high factor of safety for such ahigh g centrifuge in a simple and economical manner, effective in caseof breakage while operating, and to also control the manner of failurein a novel way.

Additional ob ects, advantages and features of invention reside in theconstruction, arrangement and combination of parts in the apparatus, andthe steps of procedure involved in the embodiment and practice of theinvention as will be set forth. apparent, or understood in or from thefollowing description and accompanying drawings wherein:

Figure 1 is a front e evation of an exampleo'f apparatus constructed inaccordance with the invention partly in section and with parts brokenaway, a diagram of a stroboscopic device being imposed thereon;

Figure 2 is a fragmentary vertical section in a plane with the mainshaft, partly diagrammatic;

Figure 3 is a fragmentary section of the tension rods.

Figure 4 is a detail elevation of a possible mounting of thestroboscopic magnet and armature bar;

Figure 5 is a schematic diagram of the centrifuge system, withelectrical circuits;

Figure 6 is a diagram of a possible modified circuit for thestroboscopic device.-

Referring more particularly to the drawings, there is illustrated acasing ill of generally cylindrical form, having small extent in thedirection of its axis. It may be closed at back and front with accessopenings and closures as at II in Figure 1 for the front, and otherwisearranged but not shown at the back. The main circular bounding part E2of the case is a double wall structure of ply wood or thin sheet metal.Principal dependence for safety is placed in a filling of packed sand I5between the two walls named, this body of sand having a radial extent ofeighteen inches in one embodiment. The annular enclosure may measureabout forty-eight inches in inside diameter and the radius of the armsof the centrifuge to be described has been in the neighborhood of twentyinches. The fore and aft measurement of the case in that part whichencloses the rotating arms of the centrifuge may be fifteen inches ormore or less, determined by a rear wall plate l t and a front wall I'!,the latter having a horizontal opening ll coincident with the diameterof the case. On this a rectangular frame is mounted including horizontalguides 18 in which heavily glazed doors H] are slidable, affording ampleaccess to parts of the apparatus for the uses intended, and permittingready observation of articles under test.

The apparatus may include a main driving motor 20 which may beconventionally mounted rearwardly of the rear plate IS, with its shaft2| as the main shaft of the apparatus extended through a small openingin this plate. The motor shaft 2| is considerably elongated, so as toaccommodate the hub of the centrifuge, two or more small generators andslip rings, all to be described.

In the present instance the centrifuge comprises a rotor having a hubbody 22 of substantial length keyed to the shaft 2| and including aheavy integral planiform head plate 23 at its outer end Within the caseIt. The hub is supported in a conventional bearing 24 on a bracket calseats 28 spaced at opposite sides of the axis of the axis of the hubarranged and shaped to receive parallel rods 29, the paired mutuallyadjacent ends of which constitute respective arms 30 of the centrifuge.At their middles the rods are slightly reduced in cross section byrespective :2.

encircling notches SI and on the hub two small radial ribs 32 are formedon a diametrical line at right angles to the seats, one in each seat 28,fitted to a respective notch 3! of the adjacent rod. A clamp 33 isfitted over each rod, engaged in the notch 3| and secured by bolts 34engaged through shanks of the clamps and in the flange 23. By this meansthe rods are held securely in a permanent relation to the hub; and-whichis a most important feature of safety-by proportioning the rods andnotches so that the minimum cross section is designed to sustain themaximum stresses which are safe, involved by the maximum speed ofrotation for which the machine is designed, with a proper tolerancemargin, in case of accident, or run-away, if the arms begin to fail bylongitudinal stresses beyond the elastic limit of the reduced crosssection of either rod, it will quickly break at the reduced part and itsload applied to the other, breaking that also, so that the whole arm isreleased. One arm being so freed, the reduced parts of the rods of theother arm will permit it also to draw away from the clamps, relievingthe centrifuge hub of its load. Damage is thus minimized as to motor andshaft and other parts on the shaft; and failing of parts which are notimmediately severed is avoided.

The rods 29 have in one embodiment consisted of one inch diameter coldrolled steel, they are for convenience all-thread stock with right-handthreads on one and left-hand threads on the other although otherexpedients may be adopted if preferred. At the extremity of each arm across plate 35 is mounted, receiving both rods therethrough and securedby nuts 36 on each rod at opposite sides of the plate. On the inner sideof one plate there is provided a receptable and specimen retainer 31,while a counterweight holding device 38 is provided on the oppositeplate 35.

An H-shaped frame 40 has its parallel end members mounted on the rodsintermediately of the length of one arm 30, in the present instance thatarm which carries the counterweight mounting, the middle bar 39 of thisframe thus extend ing longitudinally of the arm midway between th rods29. The end members of the H-frame are engaged on the rods in the samemanner as the plates 35 and held rigidly in place by similar nuts.

Concentric with the axis of the hub a small reversible motor 4| ismounted on the hub, driving a radial shaft 42 mounted in conventionalbearings on the hub and on the H-frame. The motor 4| may be of a slowspeed type or a reduction gearing 4| may be used between it and theshaft 42. At its outer end the shaft has fixed thereon a gear 43 of alength along its axis nearly equal to that of the frame 35. On each rodwithin the length of the frame 49 there is a balancing nut 44 havingfixed thereon concentric with the rod a gear 45 of sufficient radius tomesh with the gear 43. The two gears 45 and nuts 44 are in the sameplane normal to the rods, so that when the gear 43 rotates the nuts willbe operated thereby to move axially in the same direction,longitudinally of the arm 30. The motor 4| heretofore used has been aG-volt D. C. motor, its leads Ma being extended through a hollow outerportion of the main shaft 21 to slip rings 46 carried by the shaft 2|with which there are engaged stationary brushes 4'! in a control circuit41' exteriorly of the case (0. This circuit includes a manual normallyopen reversing switch 48 in the output circuit of a rectifier 49connected in parallel across the 6-volt A. C. line 53 from the secondaryof a step down transformer 5|.

'A small D. C. magnet generator 52 is mounted on the main shaft back ofthe case l0, which is utilized to obtain throughout operation of thecentrifuge a direct reading of the acceleration to which the test objectis subjected. This is achieved by connecting the armature leads to athermocouple 53 and meter 54- as in Figure 5. The output current of thistype of generator is directly proportional to the speed of the driveshaft, but the reading of a meter associated with a thermocouple isproportional to the square of this current, and thus in this use to thesquare of the speed. Since the acceleration is also proportional to thesquare of the speed, the thermocouple meter can be calibrated with alinear scale in terms of the acceleration to which the test object issubjected. The actual calibration has been in terms of g, thegravitational constant, and the meter in this instance becomes a gmeter.

For correction of the readings rendered by the g meter duplicatevariable resistances 55, 55' are alternatively included in the g metercircuit by means of and at respective closed positions of one side of adouble throw switch 56. The other blade of this switch operates as asingle pole double throw switch in shifting from volt potential to 220volt potential in the line to the main driving motor 20 for starting orthe reverse in stopping the machine, as will be eX- plained. In additiona conventionally used variable resistance 55 forms a part of the meter54.

For checking the accuracy of the readings thus obtained a small 2-poleGO-cycle, A. C. generator 51 has its armature mounted on the main shaftand its output coupled across the secondary output of the transformer 5|through a potentiometer 53, a neon discharge tube lamp 59 being coupledin: series. in the output .oi thiscgeneratom. The potentiometer may 1 be'used lto wprovide a voltage component at the tube bs-motisufilcientvtoproduceta normal illuminating discharge; and operation of thegenerator mayrbesusedztorsupply: toi-the tube avoltage componentwhichfistalso: below the'required potential, but whenzztheaaloternations'oi the generator-'51 coincide with.those=.: of theazinducedcurrents from thetransformer 5| the-lamptwill light to adesiredbrillia'nce: But when-tithe alternations thereofare-in.180::degree relation to those of the. transformeroutput, the...lamp will be extinguished... Similar coincidences inreither' case-and:corresponding:la:mp func tions:will.occin"- as the speed'z'oftheagenerator equals mul iples of. sixty and: by noting these: andthegreading of the g meter azclosezapproxima-t tien of correct readingsmay beobtainedabyad-: justments 55"wilenindicated; Other lltlilZZt-mtionszoi t ett-Jo'sourcesfil and filmayibe carried out-for similar orother, purposes;

For stopping. such; a. centrifuge."operatingl at. times *atLlOO-J g.- itis. desirableto usetaibraking: means, which may includev a motor;fiillihaving: itsarmature mounted onior geared .to."the.2shaf.t' ofmotor The motor fiil'may'be'iconnectedl across the llo volt service linethrough. a switch! 5i and rheostat suitablyto decelerate-thecemtriiugel: Alternatively or together therewith .a: mechanical brake 2'?may be used," ofanyz'convene tional form, the drumilliizoiwhicwmayrbefixeds. onthe hub of the ;centri-fuge,. :so: that braking stress torueof momentumofthe centrifugeis removedirom shaitoiJthe=-drivingcn'iotorx The details of the brake are snotzshown'. eXs.cept schematically as. in Figure 5;. and; fragmens tarily in Figure 2.

Totenable observationoiztestpobjects throughout the course of the testan automatic strobescop-ic device is provided comprising agaseousdischar e tube (Figures 1 and 6), mounted. on the case it or on therotor as hereinafter indi-. cated. This tube may be one of the neon orother commercial types now available.

A ermanent magnet til is provided, consistingof a core awindingfi'ttherea-roundr and..for.e: :ample shown fixed-entirebackrwallz of the in Figure l, and :on-..the arm of. thetcentrifugerotorbetween the. axis of rotation:-

of "the device the specimen-holder-there n=:-

frame 58 similar to the H-frame 40, and similarly mounted and secured onthe rods 29.

Its mirLle member 59 is a radial iron bar mounted so that in rotation ofthe centrifuge it will move close relation to the magnet 66, and producea fluctuation of the normally static magnetic field therearound, thusproducin momentarily an alternating current in the Winding and circuitIll leading therefrom to the lamp B5. The magnet bar is narrowed incross section on one transverse axis and its major transverse axis is inradial relation to the axis of the centrifuge. If desired the extremityof the bar magnet may be brought to a radial knife edge and the bar 69similarly shaped on the side next the magnet so that the alternation inthe magnet flux will occur in an extremely short time. If desired aconventional means may be employed in the circuit i0 so as to utilizethe flow in one direction only incident to the alternation produced oneach passage of the bar so that the lamp 65 will be illuminated onlyonce. Electronic circuits suitable for the purpose are common and wellknown. One example is formally illustrated in Figure 6, where a diode i5is shown in circuit with lamp 65.

As there will be angular"differencesofiposition speedsg: due to counterE. F. in -the.,:winding:- 2.

5 5 i and magnetic reluctance, inorder to regulate :fiuxi' movements andresultant current .fiow in rela-t tionzto-theposition of the specimenandto. more: certainly time the illumination while ,the holder;- 3? isin'ga' convenient positionior obscu ation, the.)

alo imagnetcand.ivinding may be mounted-as awunit":

adjustable along a track segment ill on the back: plate: l9. concentricwith the axis of the rotor; 1. to permit' adjustment :of the magnet sothat. the); lamp may be energized-whilethe specimen holders" :15ais inthe desired position.

In the operation'of the-machine; it maybe started;by:throwing theswitch56 (Figure 5) to: the. right, connecting the driving motor '20across: the volt circuit at one side of the three Wire 1 ml). C. powersupply '82 and a potentiometer I3 used to develop torque gradually inthe motor. A field circuit rheostat it may also be conven:-. tionallyused to control speed in part for;fine.'- adjustments of speed. When thepotentiometer? :25;.,has been moved from zero potential position to its;llorvoltposition the motor will operate; at about half'its possiblespeed. Fo'rfurther accel-.- erationz-the switch it is opened,the.potentiome-;- ter-broughtquiclrly to its zero positionand'the;

- 30n-SWillChr55mOVedt0 its alternate position at-the.:';

left in Figure 5. This connects the motor across" the'230 volt servicewith the potentiometersrinaiseries withthe motor. This potentiometerfunc-..- tioning now as a simple rheostat, by againmova 35: ings the.armzof the potentiometer to. highiposi tion, the motor :ishrought tofull speed.

The functioning of the. g. meter,-balancin'g mo toryxandsynchronizinglamp '59-, will be understood fromzthe preceding'description'of their. use

and .functions;-and effects of the rcentrifugerron.

specimens are apart from the invention.

In stopping the rotor, a reversal of the start-s ing steps is firstcarried out which effectsdynamic braking. in :the motor ZEIRand thebrake: Bil'ior r 21, or: both may be: operated as before-described. Asbefore indicated, the brake motor 60 may be omittedandonly amechanicalbrake -'utilizedfi inrconjunction with dynamicbraking manifest.v inmotor 2 I];

In case either rod 29 is subjectedto radial or other stress beyond itselastic limit While in operation, it will become severed by localizedfailure at the part 3!. This frees both ends of the broken rod and atonce adds their mass and that of parts of the other elements of therotor to the load sustained by the remaining rod, causing the latter tofail before material flailing of partly severed parts occurs and themachine saved from racking damage by extreme unbalanced centrifugalforces. The freed parts will penetrate the inner circular Wall plate ofthe case and will become embedded in and held by the mass of packed sandI5 without other extensive damage.

The driving motor may be a 2 horse power conventionally wound compoundtype having a normal full-load operating speed of at least 1400revolutions per minute. The latter speed produces 1000 g at 18 inchradius, which is the approximate radius of the path of a sample in themachine. The proportions named give a factor of safety of approximately3 to l for a one pound sample. Special alloy steel in the rods wouldgreatly magnify the safe load and margin of safety.

The magnet and lamp may be mounted either on the case or otherstationary part as described, or the lamp may be mounted on the arm 30adjacent the specimen and the circuit extended thereto conventionally.Thus one or more sets of slip rings H may be provided from which leads18 are extended through the shaft 2| and to a junction box and lampmount 1'9 on the arm 30 beside the specimen holder 31. This may be usedas part of the circuit 10, or may be used alternatively orsimultaneously to effect connections with a specimen by which electricalimpulses, current, or potential may be communicated to or from thespecimen and apparatus outside the case ID.

The magnet and its winding and the armature bar may be transposed ifdesired to simplify the lamp circuit avoiding need of the slip rings inthe circuit. The execution of this expedient is within the skill of theworker in this art and therefore is not illustrated. Alternatively alsothe magnet if stationary may be without wind-- ing, and instead thewinding placed around the armature bar 89 in the circuit 18, so thatflux drawn by the bar will cut the winding.

While I have disclosed with particularity a specific construction of oneembodiment of the invention, it will nevertheless be understood thatthis is purely exemplary, and that various changes in the construction,substitution of materials and equivalents mechanical or otherwise may bemade without departing from the spirit of the invention set forth in theappended claims, wherein:

I claim:

A centrifuge comprising a rotor hub, a rotor frame thereon comprisingparallel rods in the plane of rotation of the rotor each of said rodsbeing reduced in cross section at their middles, mounting means on thehub fitting into said reduced parts, a sample mount at one end of saidframe, and counterbalancing means on the opposite end of the frame.

2. A rotor device comprising an axial hub, a rotor rod releasably fixedthereon having opposite end portions extended radially, said rod beingreduced in cross section at its mid part at the hub mounting means onthe hub fitting into the reduced parts of the rod to hold the rodagainst sliding movement therein, said reduced part being adapted tofall within the mounting means under excess stress, whereby the two endsof the rod are freed for outward movement from the mounting means.

3. In a centrifuge a rotor, a threaded shaft attached intermediate itsends to said rotors, an interiorly threaded member engaged on one end ofthe shaft, a test sample holder on the opposite end of said shaft, areversible motor axially located on the rotor, operative connectionsbetween the motor and interiorly threaded member to rotate the same onsaid shaft, and a normally open operating circuit for said motorincluding a reversing switch.

4. In a centrifuge, two relatively rotatable members, one of which is astationary case having a view opening, and the other a rotor revolubletherein, generator elements comprising a permanent magnet fixed on oneand an armature bar fixed on the other of said members so that one willmove close past the other in operation of the rotor, an inductivewinding around one of the last named two generator elements, a testsample holder on the rotor, an electric lamp located to illuminate thesample holder in at least one position in its rotation with the rotor,and a circuit connecting the lamp and said Winding, said lamp andcircuit being constructed to produce stroboscopic illumination of asample carried by the sample holder in response to current induced insaid winding by relative passage of said magnet and armature bar.

5. In a centrifuge, a rotor, a measuring instrument comprising a directcurrent generator, synchronized with the rotor, a thermocouple in theoutput circuit thereof and a potential meter in response relation to theoutput of the thermocouple calibrated in units of g.

GEORGE B. ENGELHARDT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,608,817 Russell et al Nov. 30,1926 1,711,101 Shanck Apr. 30, 1929 1,849,831 Hewlett Mar. 15, 19321,854,949 Mead Apr. 19, 1932 2,396,678 Bucky Mar. 19, 1946

